Airtight terminal element having visibly contacting parts



Dec. 27, l 955 \nuummm D. J. ZIEHR AIRTIGHT TERMINAL ELEMENT HAVING VISIBLY CONTACTING PARTS Filed Dec. 20, 1951 United States Patent AIRTIGHT TERMINAL ELEMENT HAVING VISIBLY CONTACTING PARTS Donald J. Ziehr, Milwaukee, Wis., assignor to A llis- Chalmers Manufacturing Company, Milwaukee, Wis.

Application December 20, B51, Serial No. 262,524 2 Claims. (Cl. 174-75) This invention relates in general to insulating bushings for electrical translating devices and particularly to the terminal elements of such bushings.

Transformers or other electrical apparatus have insulating bushings which not only are subjected to temperature changes because of the current through the leadout of the bushing but frequently the transformers are outdoor installations and are exposed to weather and subjected to ambient changes through a considerable range. These changes in temperature may result in so-called breathing of the bushing permitting air to get into the bushing. If this breathing action does occur, the air which will get into the bushing will, upon lowering of its temperature, result in condensation on the conductor and terminal parts, thereby corroding some of the parts and locking them together. These difiiculties which result from breathing action may be prevented if the terminal element provides a seal for the conductor so that air cannot pass between the parts of the terminal element.

In order to avoid these difiiculties, an insulating bushing embodying this invention is provided with a terminal element which has metal to metal contact between the parts thereof. The metallic contact between the parts is visible in order that the assembly of the terminal element be foolproof and that the element be airtight. In addition, the metallic contact between the parts made according to the teaching of this invention protects the gaskets between parts of the element from weather and limits the compression of those gaskets to a predetermined amount. Yet, the assembly of the terminal element including the clamping of the conductor in the terminal element to prevent its rotation does not impose stresses on the porcelain of the insulating bushing.

It is therefore an object of this invention to provide a terminal element for an insulating bushing in which the conductive parts of the element are in conductive contact with each other and with the conductor within the element.

Another object is to provide visible metallic contact between conductive parts of a terminal element for insulating bushings.

Still another object is to provide in a terminal element, an assembly which is simple, foolproof and airtight.

And another object is to provide metal to metal contact between the parts of the terminal element to seal the element while utilizing the metallic contact between the parts to control the compression of gaskets included in the element.

And another object of the invention is to provide a sealed terminal element with metallic contact between the conductive parts, controlled compression of the gaskets, protection of the gaskets from the Weather and minimum stress on the porcelain of the insulating bushing.

Objects and advantages other than those above set forth will be apparent to those skilled in the art from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 is a view in section of part of an insulating bushing embodying this invention;

Fig. 2 is an elevation view of the stud attached to the conductor inside the bushing shown in Fig. 1;

Fig. 3 is a top view of the stud shown in Fig. 2; and

Fig. 4 is a plan view of part of the cap on the insulator.

Numeral 11 designates an insulating bushing which is shown and described as being in an upright position although it may stand in any position in a translating device. The porcelain tube 12 of the bushing has a passageway 13 and a petticoated exterior surface 14. The upper end of the porcelain has a thickened wall section to provide a flange 15, and the upper end of the passageway is closed off by a one piece metallic cap 20 which is attached to the porcelain.

In this instance the cap 20 is of a relatively soft conductive material, such as copper, and has its outer edge portion turned down around the flange of the porcelain to which it is sealed. The intermediate portion 21 of the cap is ring shaped and extends across the wall section of the end of the porcelain, and a gasket 22 is confined between the ring shaped portion and the flanged end of the porcelain. The inner portion 23 of the cap is washer shaped and extends across the passageway of the porcelain tube. The washer shaped portion has a central opening 24 for accommodating a leadout of a conductor and has offset apertures 25 for accommodating locking protuberances on the leadout. Those apertures may, as in this instance, be formed as notches in the opening 24. The washer shaped portion is axially spaced from the ring shaped portion and is disposed beyond the end of the porcelain tube.

Extending longitudinally of the passageway of the porcelain tube is a conductor 30 which is shown as being spaced from the inside wall surface of the tube. To the upper end of the conductor there is attached a leadout structure which in this instance is stud 31. The lower end of the stud forms a socket or spoon type recess for fixedly receiving the upper end of the conductor. In fixing the end of the conductor to the stud any suitable means, such as brazing, may be used.

The terminal element includes means for preventing rotation of the conductor within the terminal element, and in the illustrated structure this is done by locking the stud to the cap. The stud has a laterally extending shoulder 33 which abuts against the lower face of the cap, and upstanding from the shoulder are protuberances 34 which extend into the offset apertures 25 in the cap to thereby lock the stud and conductor against movement.

The upper portion 32 of the stud is threaded and extends through the central opening in the cap. A base nut 40, which has an angular outer edge for a wrench to engage, is screwed on the threaded portion 32 of the stud. The bottom or lower face of the base nut has two coaxial, axially spaced recesses which define a generally step shaped cross section. A gasket 42, of any suitable compressible material, is disposed in the larger of the two cylindrical recesses, and a metallic washer 43 is disposed in the smaller but deeper cylindrical recess. The radius of the circular opening of the washer 43 is longer than the distance from the axis of the threaded portion of the stud to the outer edges of the two protuberances shown on the shoulder of the stud and thereby provides clearance so that the protuberances may extend through the cap without coming in contact with the washer or the base nut. and the protuberances do not interfere with the firm abutment of the washer on the cap. The lower face of the nut has a depending flange which surrounds the washer. The inner bottom edge portion of that flange contains the gasket 42, and the outer bottom edge portion-of "thatflangeconstitutes'a lip' 41.

The base nut is screwed "tightly on to the top of the cap 20, clamping the cap between the bottom side of the washer 43' and'the' shoulder of the stud 31 "and abutting the lipd lagainst the ring shapedportion of'the cap. The 'uppersiirfabe 44 of the base nutis madejtop'rovide runoff of water; preferably"the upper surface" is sloped to provide'a continuous taper'from'its center tapped hole to its outer edge. 1 V

Part'of the threaded portion of the stud extends out of the 'tapped holein the .base nut, and a leadout body memben'47 of conductive material is screwed on the I thread'ed portion until the bottom circular edge 43 of the "body member makes metallic contact with the upper surface of thebase'nut. Sincethe upper surfac'eTof the basejfn ut is shown as tapered, the bottom edge' id of thebody member is shown correspondingly tapered so that'a portion of the bottom edge surface of the body member abuts a portion ofthe upper surface of the base nut. However, only the outerportion of the bottom edge of the' body member makes metallic contact with the 'upper surface of the base nut. The inner portion of that bottom edge has a recess which accommodates a gasket'49 of suitable compressible material.

In the preferred embodiment shown, the body member 47 has a cylindrical outer surface to which a U-bolt clamp 51 may be connected. And the upper end of the body member is provided with a hexagonal shaped flange 46 so that it may be turned with a wrench. The inside of the member has a threaded opening which forms a socket into which'the thread portion of the stud screws. To seal the't'err'ninal element the upper end of the body member is closed ofi. For this purpose a short stud 59 to which abypass arrester may be attached, is illustrated as fitted into the upper end of the body member and sealed thereto by silver solder or any other suitable means.

As mentioned above, the embodiment of this invention in a'terminal element results in many improvements. The gaskets between the body member and the upper surface of the base nut and between the lower surface of the base nut andthe upper surface of the cap are-confined in circular recesses by the outer depending edges of the body andbase nut, respectively. When the base nut is turned down on the cap the compression of thegasket 42 is limitedby the abutment of the outer lip 41 of the base nut against the upper surface of the cap.' Similarly, the compression of the gasket 49 is limited by abutment of the outer portion of the bottom edge of the'body member against the upper surface of the base nut.

While the washer 43 may be made integral with nut 40 or may be omitted, the washer preferably is made separate from the base nut in order to reduce-the possibility of damaging the upper surface of the relatively soft conductive material of which the cap is made. By providing a washer independent of the bottom surface of the base nut, the hard metallic base nut does not turn or screw down on the cap which is made of relatively soft metal. The washer which need not be as h'ard as the base nut will be forced down on the washer shaped portion of the cap without turning very much on the cap. instead, the base nut will turn on the washer until the washer shaped portion of the cap is clamped between the shoulder of the stud and the washer.

In the preferred embodiment, the parts are made so that when the cap is clamped with the shoulder of the stud firmly up against the lower face of the cap and with the washer against the upper face of the cap, there is a clearance between the depending lip 41.0 f the base nut andjthe upper face of the ring shaped portion of the cap. Then the base nut is farther screwed downuntil the depending lip of the nut can be seen to make metallic contact' with the upper surface of the ringshaped portion of'the cap. This movement causes the inner portion of the cap to be tightly compressed between shoulder 33 and washer *43.

The protuberances on the shoulder of the stud may vary slightly in length, and to avoid the expense of inspecting and trimming their length to the thickness of the cap, the washer provides a clearance space for those protuberances between the cap and the bottom surface of the base nut as above mentioned.

Since the depending lip of the base nut is directly over the gasket between the end of the porcelain and the ring shaped portion of the cap, there is substantially no strain imposed on the porcelain when tightening the base nut down on the cap. Also, the conductor to which a leadout stud is attached may be locked against rotation within the porcelain tube of the bushing by the protuberances which extend into apertures in the cap so that the holding of the conductor against movement when the base nut is tightened or loosened imposes no appreciable strain on the porcelain.

A further advantage of thi's'iinv'e'ntion is that since the conductive parts of the terminal element are in firm contact with each other and with the'conductor through the abutment of the shoulder of the stud against the cap, there is an increase in cross section of material which. may carry current and the temperature change because of the current may be reduced. 7

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to one skilled in the art that various changes and modifications may be made. therein without departing from the spirit of the invention or from the scope of the appended claims. I v v i It is claimed and desired to secure by Letters Patent:

1. A terminal element including an insulating tube having apassageway, a conductor disposed lengthwise in said passageway, a cap of conductive material fixed to the upper end of said tube, said cap'having a ring shaped portion extending across the wall section of the end of said tube and having a washer shaped portion extending across said passageway, said washer shaped portion having a central opening and an offset aperture, a first gasket between the wall-section of said tube and said ring shaped portion, a stud of conductive material attached to said conductor, said stud having athreaded portion extending through said central opening in said cap, said stud having a laterally extending shoulder at the base of said threaded portion abutting the lower face of said washer shaped portion, a protuberance on said shoulder received in said aperture. to, pr,event rotation of said conductor within said tube, a base;:nut of conductive material screwed on said threaded portion, the lower face of said nut having a cylindrical recess surrounding said threaded portion, a washer of conductive material in said recess with the lower face of saidjwasher abutting againstthe upper face of said washer'shaped portion, the radius of the opening in said washer being longer than the distance of said protuberance from the axis of said stud to provide clearance for said protuberance, the lower face of said nut having a depending flange surrounding said washer shaped portion, said flange having an outer lip making metallic contact with said ring shaped portion along an externally visibleline, the inner bottom edge portion of said flange having a recess from said lip, 21 second' gasket retained insaid recess of said flange between said flange and said ring shaped portion, said contact of said 'n'ut with said cap sealing sa'id second gasket from the atmosphereand limiting thecomp'ressi o'n' of said second gasket, said nut having a sloped upper surface, a body of conductive material having a'thread'ed socket screwed on said threaded portion, to enclose said threaded portion with the outer bottom edge portion of said body being tapered and making metallic c'o'ntactwith said uppersurface of saidn'ut along an externally. visible line, the inner bottom edge portion of said body having a recess, and a third gasket retained in said recess of said body between said body and the upper surface of said nut, said contact of said body with said nut sealing said third gasket from the atmosphere and limiting the compression of said third gasket.

2. A terminal element including an insulating tube having a passageway, a conductor disposed lengthwise in said passageway, a cap of conductive material fixed to the upper end of said tube, said cap having a ring shaped portion extending across the Wall section of the end of said tube with a central opening and an offset aperture in the inner portion of said cap, a first gasket between the end wall section of said tube and said ring shaped portion, a stud attached to said conductor, said stud having a threaded portion extending through said central opening, a laterally extending shoulder at the base of said threaded portion, and a protuberance on said shoulder, said shoulder abutting the lower face of said cap inner portion with said protuberance received in said aperture preventing rotation of said conductor within said tube, a base nut screwed on said threaded portion, the lower face of said nut having a depending flange surrounding said cap inner portion with the outer edge portion of the bottom of said flange constituting a lip making metallic contact with said ring shaped portion along an externally visible line, the inner edge portion of the bottom of said flange having a recess, a second gasket retained in said recess in said flange compressed against said ring shaped portion with contact of said flange with said cap sealing said gasket from the atmosphere and limiting compression of said gasket, a body having a threaded socket screwed on said threaded portion and enclosing said threaded portion with the outer bottom edge portion of said body making metallic contact with the upper surface of said nut along an externally visible line, the inner bottom edge portion of said body having a recess, and a third gasket retained in said recess of said body compressed against the upper surface of said nut with the contact of said body with said nut sealing said third gasket from the atmosphere and limiting compression of said third gasket.

References Cited in the file of this patent UNITED STATES PATENTS Re. 22,079 Stevens Apr. 21, 1942 1,728,952 Austin Sept. 24, 1929 l,837,375 Saurman et al. Dec. 22, 1931 2,000,688 Burr May 7, 1935 2,368,923 Hampton Feb. 6, 1945 

